We have recently developed a new technology called tissue-initiated photopolymerization, which permits direct covalent integration of a polymer into collagen, that been shown to mechanically stabilize hydrogel-cartilage interaction. Furthermore, the technique we have developed, tissue-initiated photopolymerization, allows in situ hydrogel formation to occur without an exogenous photoinitiator, improving biocompatibility. A patent application covering this invention has been filed. There are several envisioned applications of this technology, and the objective of this proposal is to develop the first application, to provide a method for annealing of grafted cartilage and tissue engineered cartilage constructs to the surrounding host articular cartilage. It is anticipated that this will provide a stable implantation of grafts (for example, autologous or allogeneic cartilage-bone grafts, or tissue engineered cartilage constructs) into the articular defect site, and that this will substantially increase long-term performance of the implanted materials. The overall hypothesis for this Phase I and Phase II program is that native articular cartilage and tissue-engineered cartilage can be successfully integrated into the surrounding tissue to repair focal articular defects. The work in the Phase I grant will demonstrate feasibility of the photopolymerization to bond native cartilage and tissue-engineered cartilage by optimizing (a) the pretreatment of cartilage constructs and surrounding extracellular matrix, and (b) the photopolymerization. Specific Aim 1: Complete development of methods to photopolymerize cartilage and cartilaginous extracellular matrices. The data generated will identify the parameters to be used in Specific Aim 2, for the optimal method to be identified, based on mechanical properties of the annealing site, and cell viability at and near the annealing site. Specific Aim 2: Select the optimal method for tissue-initiated photopolymerization. A factorial design of experiment will be used to optimize the variables, to provide (a) tensile properties at the junction approaching hose of native articular cartilage, and (b) cell viability near the annealing site. These in vitro studies will demonstrate whether this approach is feasible for testing in in vivo situations (Phase II application).